1. Field of the Invention
The present invention relates to heat sinks for light emitting diode (LED) lighting and a vehicle LED lamp that includes an LED element as a light source. The heat sink dissipates heat, which is generated when an LED lamp emits light, through radiation to a closed space therearound.
2. Description of the Related Art
Lighting that uses LED elements, which have a long life and feature low power consumption, as its light source has been gradually penetrating to the market. Nowadays, vehicle LED lamps (lighting fixtures for a vehicle and head lights for a vehicle) such as vehicle head lights have been drawing attention in particular among a variety of LED lighting fixtures, and replacement of conventional light source with the LED elements has begun. As application of such vehicle LED lamps (LED lighting), replacement of conventional light in mounted lighting for buildings and other fields of application with the LED lamps has also begun.
However, LED elements as a light source of an LED lamp are significantly vulnerable to heat. For example, when an allowable temperature such as 100° C. is exceeded, luminous efficiency may decrease, and the life of the LED elements may be affected. In order to address this problem, heat generated when the LED element emits light needs to be dissipated to the surrounding space. Thus, an LED lamp is typically equipped with a large heat sink.
In many cases, related-art heat sinks for an LED lamp (LED lighting) use aluminum die-casting products or extruded aluminum products formed of aluminum (including aluminum alloys) (see Japanese Unexamined Patent Application Publications No. 2007-193960, No. 2008-7558, No. 2009-277535, and No. 2010-278350). As illustrated as an example in a perspective view in FIG. 14, these related-art heat sinks are generally include a base portion 30 and fin portions 40. The LED element L (light source) is secured on the front surface side of the base portion 30. A plurality of the fin portions 40 that protrude from the rear side of the base portion 30 are spaced apart from and parallel to one another.
In order to integrate a heat sink for an LED lamp with a vehicle LED lamp (vehicle lighting fixture), a lighting unit (LED lamp unit) is typically disposed in the following structure: a light chamber is defined by a front surface lens and a housing, in which LEDs that serve as a light source is supported (see, for example, Japanese Unexamined Patent Application Publications No. 2008-130232 and No. 2009-76377). Specifically, in an example as illustrated in FIG. 15, such a lighting unit is disposed as follows: that is, in a vehicle LED lighting fixture 51, a light chamber 54 is defined by a front surface lens 52 and a housing 53, and a lighting unit 55 is supported in the light chamber 54.
The lighting unit 55 includes an optical system and a heat dissipating system. The optical system includes an LED element (light source) 56, a mount plate 57, a reflector (reflection plate) 58, a lens holder 59, a shield 60, and a projection lens 61, thereby forming a projector lamp. An LED element 56 circuit board is disposed on the mount plate 57. The reflector 58 is connected to the mount plate 57. The lens holder 59 is connected to the reflector 58. The shield 60 extends upward from an inner bottom surface of the lens holder 59. The projection lens 61 is supported by the lens holder 59.
The heat dissipating system includes the mount plate 57, a heat sink 62, and the reflector 58. The LED element 56 circuit board is disposed on the mount plate 57. The heat sink 62 is secured to the mount plate (base 57). The mount plate 57 and the heat sink 62 are integrated with each other so as to form a heat dissipating member 63, to which the reflector 58 is connected. The base 57, the heat sink 62, and the reflector 58 are formed of one of the following metal materials: Al, an Al alloy, Cu, and a Cu alloy.
In the optical system, when the LED element (light source) 56 is turned on and emits light, light travels from the LED element 56 toward a light reflection surface 64 of the reflector 58 and is reflected by the light reflection surface 64 toward the projection lens 61 at the front. An optical path of part of the light is blocked by the shield 60. The light reflected by the light reflection surface 64 of the reflector 58 and not blocked by the shield 60 is guided through the lens holder 59 and reaches the projection lens 61. The light is distributed in a desired manner by the projection lens 61 and projected toward the front side of the vehicle LED lighting fixture 51 through the front surface lens 52 of the vehicle.
Regarding heat in the heat dissipating system, when the LED element 56 is turned on, light is emitted and heat is generated. Heat generated by the LED element 56 (self-heating) is transferred to the board (not shown), on which the LED element 56 is mounted, conducted through the board, and transferred to the mount plate 57, on which the board is disposed. Then, the heat conducted through the mount plate 57 is transferred to the heat sink 62, which is secured to the mount plate 57. The heat having been transferred to the heat sink 62, conducted through the heat sink 62, and reached the surface of the heat sink 62 is conducted and transferred to air near the surface of the heat sink 62, and radiated to the outside of the heat sink 62 through air as a medium.